Time of metamitron application and concentration in the chemical thinning of ‘Maciel’ peach

Abstract In the peach tree cultivation, the producer has the challenge of obtaining good quality fruits and maintaining production in a balanced way over the years. Thinning favors these parameters and reduces the fruit load on plants. Manual thinning commonly practiced on peach trees requires high labor and increases production costs. Chemical thinning as an alternative to manual thinning, which depending on the species, time and concentration, has demonstrated high efficiency. The aim of this study was to evaluate the effect of metamitron applied at different seasons and concentrations on the chemical thinning of peach trees in southern Brazil. Experiments were conducted in a commercial peach orchard (‘Maciel’ cultivar), in the municipality of Morro Redondo, Rio Grande do Sul, Brazil, during the 2015 and 2016 harvests. In experiment 1, metamitron at concentration of 200 mg L-1 was applied at 20, 30, 40, 50 and 60 days after full bloom and manual thinning performed at 40 days after full bloom. In experiment 2, metamitron was applied at concentrations of 100 mg L-1, 200 mg L-1, 300 mg L-1 and 400 mg L-1 and manual thinning at 40 days after full bloom, in addition to control plants. Fruit abscission, fruit set, total number of fruits per plant, yield per plant, average mass and fruit diameter were evaluated. Metamitron at concentration of 200 mg L-1 has thinning effect when applied before 40 days after full bloom. Metamitron concentration of 100 mg L-1 applied at 40 DAFB promoted fruit abscission superior to manual thinning. Therefore, the application of metamitron to ‘Maciel’ peach trees close to full bloom at concentration of 100 mg L-1 results in thinning practice similar to manual thinning.